Performance of the Innova SARS-CoV-2 antigen rapid lateral flow test in the Liverpool asymptomatic testing pilot: population based cohort study
Study (n=5869) found Innova LFT results were positive for most people with high viral load (likely to be infectious) who tested positive using RT-qPCR, whereas results were negative for most people with viral load <104 RNA copies/mL (expected to be less infectious).
Source:
British Medical Journal
SPS commentary:
The researchers suggests from these data that the Innova LFT seems, in combination with other health protection measures, to be a valuable tool in wider public health responses to covid-19 for identifying those with higher viral loads who are more likely to be infectious but do not report classic symptoms. They add that to maximise the value of LFT, care should be taken to train test operatives, communicate the meaning of results to tested people, target testing with reference to background case rates, and avoid single LFT results for access to vulnerable settings (such as care homes) where the consequences of infection are severe (unless comprehensive additional risk reduction measures are considered).
According to an editorial, the most important question about community mass testing is whether it works to reduce transmission, for which the answer is not yet known. It suggests a study that randomised the offer of repeated testing in asymptomatic people versus no offer of testing by geographical area would be best placed to answer that, and any country considering implementation of mass testing would do a great service to knowledge by randomising the roll-out. It notes that the impact of testing depends on more than the accuracy of the test; other factors at play include low adherence to self-isolation in those testing positive, limited uptake of testing skewed towards those at lowest risk of SARS-CoV-2, misuse of lateral flow tests (people with symptoms using the quicker lateral flow tests rather than the more sensitive PCR tests), and false negative rapid test results giving false reassurance.